1. Field of the Invention
The present invention relates to an apparatus for electrically operating a circuit breaker in which a spring is compressed by means of an electric motor to store mechanical energy and then the mechanical energy is discharged to throw the circuit breaker.
2. Description of the Prior Art
One such a conventional apparatus for electrically operating a circuit breaker will be described with reference to FIG. 13 to FIG. 16. FIG. 13 is a side view of the apparatus in which the spring has fully discharged mechanical energy thereof; FIG. 14 is a cross sectional side view of the apparatus in which the spring is being compressed; FIG. 15 is a cross sectional side view of the apparatus in which the spring has been fully compressed; and FIG. 16 is a general top view of FIG. 15.
Referring to the diagrams, a frame 3 of a prior art apparatus is secured to the front portion of a circuit breaker 1. An electric motor 4 is secured on the frame 3 and the rotation of the motor 4 is transmitted to a main shaft 6 which drives a ratchet gear 5 via a reduction gear 8. The main shaft 6 is connected to the motor via a one way clutch 7. The ratchet gear 5 is provided with a cam 11, which rotates together with the ratchet 5 in a unitary motion. The cam 11 engages a roller 17 which is journaled for free rotation on a side wall 12b of a slider 12 for causing the slider 12 to slide on a guide rod 14 which is secured to the frame 3. The guide rod 14 extends through a rod insertion hole 15 provided on a front wall 12a of the slider 12.
Thus the slider 12 is guided by the guide rod 14 to slide thereon. A spring 16 is attached to the guide rod 14. The slider 12 is provided with two handle drive pins 13a and 13b to drive a handle 2 of the circuit breaker 1 therebetween, the drive pin 13a for throwing the handle 2 into the ON position and the drive pin 13b for throwing the handle 2 into the OFF position. When an OFF signal is supplied, the motor 4 drives the main shaft 6 in rotation via the ruduction gear 8 and the one way clutch 7; thereby causing the ratchet gear 5 to rotate in a direction of an arrow A in FIG. 13. The cam 11 also rotates with the ratchet gear 5 in the direction A, then comes in contact with the roller 17 for causing the slider 12 to slide in a direction of an arrow B. At this time the slider 12 compresses the spring 16 as shown in FIG. 14, while also throwing the handle 2 into the OFF-position of the circuit breaker 1 by means of the handle drive pin 13b. A stop lever 19 is swingably mounted on the side wall 12b of the slider 12. The side wall 12b is provided with a guide and stopper pin 23 to engage with an elongate hole of the stop lever 19. The stop lever 19 is urged against the side wall 12b by means of a twist spring 20. The stopper pin 21 of the cam 11 engages with a bent portion of the stop lever 19 for causing the stop lever 19 to swing against the twist spring 20. Moving in the direction B, the slider 12 approaches a position where the circuit breaker 1 becomes OFF, and then the stop lever 19 engages with an actuating lever of a limit switch 18. When the ratchet gear 5 further rotates, the cam 11 causes the stop lever 19 to swing in a direction of an arrow C against the twist spring 20. In this manner, the stop lever 19 actuates the limit switch 18 to stop the motor 4. The stopper pin 23 terminates swinging motion of the stop lever 19 in a condition shown in FIG. 15. Thus overrun of the cam 11 is prevented. The slider 12 is held by a latch mechanism 22 at a position shown in FIG. 15. The latch mechanism 22 is to hold both the slider 12 and the spring 16 at a position at which the spring 16 remains fully compressed, and is formed by a link 22a of the slider 12 and a latch (not shown) of the frame 3. Additionally the ratchet gear 5 is provided with a fixed pawl to prevent reverse rotation thereof.
In FIG. 16, operating a manual opration handle 9 in a pumping fashion permits rotation of the ratchet 5 in the direction A in FIG. 13 thus the off-operation of the circuit breaker can also be effected in a manner similar to the case operated by the motor 4. In the manual mode, the motor 4 is disconnected with the aid of the one way clutch 7.
The ON-operation of this conventional apparatus to make the circuit breaker ON will now be described with reference to FIG. 15 which shows the OFF state of the circuit breaker 1. When the latch 22 is actuated upon occurrence of the ON signal, the slider 12 is set free from being latched and the stored mechanical energy of the compressed spring 16 is released. The slider is then pushed out to slide in a direction of an arrow D while at the same time the stop lever 19 moves in the direction D, during which the slider 12 switches the handle 2 to the ON position by means of the handle drive pins 13a as shown in FIG. 13.
With the conventional apparatus for electrically operating a circuit breaker thus far described, it is necessary to stop the motion of the cam 11 at a specific location so that the cam 11 and the roller 17 are positioned within a predetermined area after the OFF-operation is completed. For this purpose, a special type of a brake such as reverse rotation was applied to bring the motor 4 to a stop, or mechanical strength of the bent portion was increased to stop the further swing of the stop lever 19, thereby preventing overrun of the cam 11 due to inertial rotation of the electrical motor 4. Also in the case of malfunction of a limit switch 18 which operatively engages with the cam 11 to switch off the motor 4, the stopper portion of the cam 11 is damaged or the motor 4 burns out due to overload.